1. Field of the Invention
The present invention relates to a conveying apparatus and, in particular, to a frog-leg type conveying apparatus for conveying an article by those arms actuated like frog legs.
2. Description of the Related Art
Conventionally, a semiconductor device manufacturing apparatus often employs a frog leg type conveying apparatus for conveying a semiconductor wafer. The conveying apparatus comprises a pair of first arms rotated with two first supporting points as their centers, the two first supporting points being provided on a base in a spaced-apart relation; a pair of second arms rotated with two second supporting points as their centers, the two second supporting points being provided on the end portions of the first arms; and a support member having two third supporting points for rotatably supporting the end portions of the two second arms and supporting a semiconductor wafer to be conveyed. In this conveying apparatus, a semiconductor wafer supported on the support member is moved by extending and contracting the first and second arms with the first and second supporting points as articulated points. This type of frog-leg type conveying apparatus is disclosed in Published Unexamined Japanese Patent Applications 60-183736 (PCT/US84/00185) and 61-87351.
The above Japanese Patent Application 61-87351 discloses a frog-leg type conveying apparatus for moving the support member away from the base when the first and second arms are contracted into a superimposed state.
Theoretically, the support member for supporting a semiconductor wafer can be moved away from the base by moving the pair of first arms through an angle of 180.degree.. Generally, a scalar robot is used for this type of conveying apparatus.
Since the scalar robot takes up a greater occupation area, it is not appropriate to locate the robot in a load/lock chamber of the semiconductor wafer treating apparatus which has to improve its throughput.
Further, in the case where the paired first and second arms are equal in length between their supporting points, a load acts upon the arms when the paired first and second arms are brought to their superimposed position and beyond. The load involved vibrates the conveying apparatus and produces a defective driving operation, preventing a smooth conveying operation.